Modern networks are responsible for interconnecting computing devices operable to exchange data. Data may be exchanged from circuit to circuit on a common circuit board or from circuit board to circuit board along a common backplane, for example, in a computer or server. In some implementations, data may be exchanged over long distances, for example, from a travel agent's computer to an airline server on a cloud network.
Data can be transferred in the form of digital (e.g., bits and bytes) or analog (e.g., radio frequency (RF)) signals. Data communication systems may physically transfer the data from transmitter to receiver via wired and/or wireless links. Further, some data communication systems may need to operate within one or more frequency bands to match a transmit frequency to a receive frequency.
Some transmit or receive circuits that operate over a range of frequencies may use a phase-locked loop (PLL). In general, a PLL may be a frequency control circuit that generates an output signal whose phase is related to the phase of an input signal. A PLL may be formed from a frequency oscillator (e.g., a voltage-controlled oscillator (VCO)) coupled with a phase detector in a feedback loop. The oscillation frequency of the VCO may be varied by adjusting a variable capacitor within the VCO. A VCO may be an inductor-capacitor VCO (LC VCO) or a transformer-capacitor VCO (TC VCO). The inductor or the transformer may affect the oscillation frequency of the VCOs.